Compared to conventional, ecological intensive management promotes beneficial proteolytic soil microbial communities for agro-ecosystem functioning under climate change-induced rain regimes

Projected climate change and rainfall variability will affect soil microbial communities, biogeochemical cycling and agriculture. Nitrogen (N) is the most limiting nutrient in agroecosystems and its cycling and availability is highly dependent on microbial driven processes. In agroecosystems, hydrolysis of organic nitrogen (N) is an important step in controlling soil N availability. We analyzed the effect of management (ecological intensive vs. conventional intensive) on N-cycling processes and involved microbial communities under climate change-induced rain regimes. Terrestrial model ecosystems originating from agroecosystems across Europe were subjected to four different rain regimes for 263 days. Using structural equation modelling we identified direct impacts of rain regimes on N-cycling processes, whereas N-related microbial communities were more resistant. In addition to rain regimes, management indirectly affected N-cycling processes via modifications of N-related microbial community composition. Ecological intensive management promoted a beneficial N-related microbial community composition involved in N-cycling processes under climate change-induced rain regimes. Exploratory analyses identified phosphorus-associated litter properties as possible drivers for the observed management effects on N-related microbial community composition. This work provides novel insights into mechanisms controlling agro-ecosystem functioning under climate change

Phosphorus availability determines the response of tundra ecosystem carbon stocks to nitrogen enrichment.

This study was funded by NERC (NE/I016899/1) and facilitated by use of NERC facilities at Harland Huset, Ny-Ålesund and the kind support of Nick Cox and colleagues. Nancy Burns assisted with field sampling and Brodie Shaw and Rob Mills assisted with laboratory analyses. Open access via Springer Compact Agreement.Peer reviewedPublisher PD

Sensitivity and variability of soil health indicators in a California cropping system

An indicator that is used to monitor whether a management practice is improving soil health must be sensitive to management changes. However, it should not be overly influenced by variations in sampling time or location, previous crop, or annual differences in weather or operations timing. In this study, we assessed the sensitivity and variability of several soil health indicators in long-term plots under typical farming practices in a Mediterranean climate. These plots have been conventionally or organically farmed in a corn (Zea mays L.)–processing tomato (Solanum lycopersicum L.) rotation for 25 yr. We sampled in both crop phases prior to planting and midseason for two consecutive years, analyzing subsamples taken from three adjacent locations per plot. Management was the most significant factor differentiating most indicators, particularly indicators of biological processes and C accumulation. Whereas management differences were consistent across sampling times, average indicator values for a management system often varied significantly between dates and years. Crop phases, conversely, were usually similar. Accounting for soil texture increased management sensitivity for aggregate stability and most C accumulation indicators. Sensitive indicators such as mineral N, particulate organic matter C, and mineralizable C had greater subsample variability than indicators measuring large, stable pools, such as total C. Our results show that indicators relating to organic C and biological processes most strongly differentiated the two systems, and underline the importance of using consistent sampling dates. They also suggest that an indicator dataset including both stable and sensitive indicators may be the most reliable to interpret

Acid stress and compost addition decouple carbon and nitrogen cycling in an agricultural soil: An incubation study

Agricultural practices can lead to fluctuations in soil pH and salinity, likely affecting soil nutrient cycling. Compost addition may reduce the impact of these stresses, leading to more stable and resilient systems. We tested nitrogen (N) and carbon (C) cycling responses to the imposition and relief of an acute stress in an agricultural soil, and whether these responses were moderated by compost. In greenhouse pots, we mixed soil with elemental sulfur (S) and compost in a complete 2-way factorial design and incubated at ambient temperatures. Sulfur induced strong acidity and mild salinity stress. After 70 d, stress was partially alleviated by leaching with liquid lime. We took samples 21 and 42 d after S addition and one week after alleviation, measured enzyme activity, microbial biomass, and soluble organic C and N, and performed N and C cycle assays by incubating subsamples with and without ground legume residues to stimulate mineralization and microbial growth. Net N mineralization increased in response to the applied stress, and declined after alleviation. Conversely, stress reduced most C cycling indicators and inhibited nitrification. Stress limited microbial growth more than respiration. Unexpectedly, compost additions to the stressed soils consistently stimulated net N mineralization compared to stressed soils without compost. Compost thus exacerbated rather than buffered the effects of stress on net N mineralization. Compost addition did not affect microbial growth or respiration in any treatment, or how any C cycle parameter responded to stress. The decoupled C and N responses suggest that the localized stresses associated with intensive agriculture may have important implications for C and N turnover in these systems, and warrant further study. Additionally, they demonstrate that biogeochemical processes should be evaluated concurrently when accessing the effect of stressors in soil systems